/*
 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package com.sun.jmx.snmp;

import java.io.*;
import java.util.Hashtable;
import java.util.*;

/** This class is used for implementing enumerated values.
 *
 * An enumeration is represented by a class derived from Enumerated.
 * The derived class defines what are the permitted values in the enumeration.
 *
 * An enumerated value is represented by an instance of the derived class.
 * It can be represented :
 *  - as an integer
 *  - as a string
 *
 * <p><b>This API is a Sun Microsystems internal API  and is subject
 * to change without notice.</b></p>
 */

abstract public class Enumerated implements Serializable {

    /**
     * Construct an enumerated with a default value.
     * The default value is the first available in getIntTable().
      * @exception IllegalArgumentException One of the arguments passed to the method is illegal or inappropriate.
     */
    public Enumerated() throws IllegalArgumentException {
        Enumeration<Integer> e = getIntTable().keys();
        if (e.hasMoreElements()) {
            value = e.nextElement().intValue();
        } else {
            throw new IllegalArgumentException();
        }
    }

    /**
     * Construct an enumerated from its integer form.
     *
     * @param valueIndex The integer form.
     * @exception IllegalArgumentException One of the arguments passed to
     *            the method is illegal or inappropriate.
     */
    public Enumerated(int valueIndex) throws IllegalArgumentException {
        if (getIntTable().get(new Integer(valueIndex)) == null) {
            throw new IllegalArgumentException();
        }
        value = valueIndex;
    }

    /**
     * Construct an enumerated from its Integer form.
     *
     * @param valueIndex The Integer form.
     * @exception IllegalArgumentException One of the arguments passed to
     *            the method is illegal or inappropriate.
     */
    public Enumerated(Integer valueIndex) throws IllegalArgumentException {
        if (getIntTable().get(valueIndex) == null) {
            throw new IllegalArgumentException();
        }
        value = valueIndex.intValue();
    }

    /**
     * Construct an enumerated from its string form.
     *
     * @param valueString The string form.
     * @exception IllegalArgumentException One of the arguments passed
     *  to the method is illegal or inappropriate.
     */
    public Enumerated(String valueString) throws IllegalArgumentException {
        Integer index = getStringTable().get(valueString);
        if (index == null) {
            throw new IllegalArgumentException();
        } else {
            value = index.intValue();
        }
    }

    /**
     * Return the integer form of the enumerated.
     *
     * @return The integer form
     */

    public int intValue() {
        return value;
    }

    /**
     * Returns an Java enumeration of the permitted integers.
     *
     * @return An enumeration of Integer instances
     */

    public Enumeration<Integer> valueIndexes() {
        return getIntTable().keys();
    }

    /**
     * Returns an Java enumeration of the permitted strings.
     *
     * @return An enumeration of String instances
     */

    public Enumeration<String> valueStrings() {
        return getStringTable().keys();
    }

    /**
     * Compares this enumerated to the specified enumerated.
     *
     * The result is true if and only if the argument is not null
     * and is of the same class.
     *
     * @param obj The object to compare with.
     *
     * @return True if this and obj are the same; false otherwise
     */
    @Override
    public boolean equals(Object obj) {

        return ((obj != null) && (getClass() == obj.getClass()) && (value == ((Enumerated) obj).value));
    }

    /**
     * Returns the hash code for this enumerated.
     *
     * @return A hash code value for this object.
     */
    @Override
    public int hashCode() {
        String hashString = getClass().getName() + String.valueOf(value);
        return hashString.hashCode();
    }

    /**
     * Returns the string form of this enumerated.
     *
     * @return The string for for this object.
     */
    @Override
    public String toString() {
        return getIntTable().get(new Integer(value));
    }

    /**
     * Returns the hashtable of the integer forms.
     * getIntTable().get(x) returns the string form associated
     * to the integer x.
     *
     * This method must be implemented by the derived class.
     *
     * @return An hashtable for read-only purpose
     */

    protected abstract Hashtable<Integer, String> getIntTable();

    /**
     * Returns the hashtable of the string forms.
     * getStringTable().get(s) returns the integer form associated
     * to the string s.
     *
     * This method must be implemented by the derived class.
     *
     * @return An hashtable for read-only purpose
     */

    protected abstract Hashtable<String, Integer> getStringTable();

    /**
     * This variable keeps the integer form of the enumerated.
     * The string form is retrieved using getIntTable().
     */
    protected int value;

}
